Mircrobial communities and metabolisms responsible for chemolithoautotrophic energy and carbon transfer at the Mid-Atlantic Ridge
Final Report Abstract
In summary, it appears that the detected chemical and microbial inter-field and intra-field variability likely also reflects short-term temporal and small spatial heterogeneity to a certain degree. However, chemical features and mixing processes in the vent biotope indeed affect the local microbes and their distinct metabolisms in a given environment. The uptake hydrogenase richness (five hydrogen-rich fluids from the ultramafic hosted Logatchev and three samples from hydrogen-poor basalt-hosted sites at 5°S and 9°S on the MAR) is likely attributed to hydrogen concentrations (as a consequence of the type of host rock) and the degree of oxygenated compounds controlled by admixture of ambient seawater. The degree of uptake hydrogenase diversification (that we could detect with the general primers used) appears to be related to hydrogen threshold values. If the hydrogen concentrations drop below a certain value, hydrogen oxidation only becomes thermodynamically feasible if coupled to electrochemically more positive electron acceptors. Within this context, the degree of admixed oxygenated seawater – diluting the reduced emissions – effects the hydrogen-oxidizing microbes threefold: (i) dilution would have a smaller impact on fluids, which are highly enriched in hydrogen (as is the case in ultramafic-hosted systems) than those, which are poor in hydrogen where the already limited amount of hydrogen would be further reduced (near or below hydrogen threshold values of certain electron acceptor processes), (ii) dilution would determine the availability of electrochemically more positive electron acceptors and (iii) the degree of dilution can determine the temperature of the emissions. On the contrary to the uptake hydrogenase diversity, hydrogen consumption and carbon fixation (fueled by hydrogen oxidizing reactions) rates can be very high using fluids originating from hydrogen-poor vents (under the conditions we applied in the incubations). Hence, the hydrogenase diversity (richness and evenness) and the hydrogen oxidizing capacity appear to be controlled to different extents by distinct parameters.
Publications
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(2009). Short-term temporal microbial and physico-chemical variability in low-temperature hydrothermal fluids near 5°S on the Mid-Atlantic Ri dge. Environmental Microbiology 11 (10) 2526-2541
Perner, M., Bach, W., Koschinsky, A., Garbe-Schönberg, D., Streit, W. R. & H. Strauss
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(2010). Geochemical constraints on the diversity and activity of H 2-oxidizing bacteria and archaea in diffuse hydrothermal fluids from a basalt- and an ultramafic-hosted vent. FEMS Microbiology Ecology 74 (1) 55-71
Perner, M., Petersen, J. M., Zielinski, F., Gennerich, H. H. & R. Seifert
